Re: [PATCH] rhashtable: fix for resize events during table walk
flat view
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: 2015-07-06 13:31:01
Also in:
lkml, sparclinux
On Mon, Jul 06, 2015 at 02:01:42PM +0200, Phil Sutter wrote:
If rhashtable_walk_next detects a resize operation in progress, it jumps
to the new table and continues walking that one. But it misses to drop
the reference to it's current item, leading it to continue traversing
the new table's bucket in which the current item is sorted into, and
after reaching that bucket's end continues traversing the new table's
second bucket instead of the first one, thereby potentially missing
items.
This fixes the rhashtable runtime test for me. Bug probably introduced
by Herbert Xu's patch eddee5ba ("rhashtable: Fix walker behaviour during
rehash") although not explicitly tested.
Fixes: eddee5ba ("rhashtable: Fix walker behaviour during rehash")
Signed-off-by: Phil Sutter <phil@nwl.cc>Good catch!
quoted hunk ↗ jump to hunk
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index a60a6d3..e36b94b 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c@@ -585,6 +585,7 @@ void *rhashtable_walk_next(struct rhashtable_iter *iter) struct bucket_table *tbl = iter->walker->tbl; struct rhashtable *ht = iter->ht; struct rhash_head *p = iter->p; + void *rc = NULL; if (p) { p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);@@ -617,12 +618,12 @@ next: if (iter->walker->tbl) { iter->slot = 0; iter->skip = 0; - return ERR_PTR(-EAGAIN); + rc = ERR_PTR(-EAGAIN); } iter->p = NULL;
I think a simpler fix would be to move "iter->p = NULL" before the if statement. Thanks, -- Email: Herbert Xu [off-list ref] Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt